why no vaccine was found to prevent aids so far?

Answer 1

Well, it wouldn't be an AIDS vaccine, it would be a vaccine to prevent HIV infection... and the FDA just gave approval for human testing of a vaccine for HIV infection, so one is likely to be forthcoming very soon.

The big problems with HIV which make the road to a vaccine seem much longer than it should take are in the uniqueness of the virus.

First, we cannot instantly create a vaccine to any virus out there, no matter what type of virus it is. These things take time to make. It was years of research which led to a working vaccine for all the diseases we now vaccinate for, from polio, hepatitis, measles, mumps, smallpox, etc. Even the flu vaccine initially took several years to develop, and we have to take some time to develop new vaccines for new strains, even though we've become old hat at making them.

So, in that regard, it hasn't taken an especially long time. Twenty-five years of research may seem like a lot of time, but when you're confronted with a whole new class of disease, learning as much as we have about it in that length of time-- even as it's racing to evolve so quickly-- shows quite a bit of dedication and accomplishment.

Despite the notable fact that those researching the problem have often been crippled by prejudice and hatred on the part of those doling out the money for research, an amazing amount has actually been done in the last quarter century or so to fight this disease and ultimately defeat it.

As we get the process of creating a vaccine for this particular virus down, it will become easier and quicker for us to manufacture new vaccines to guard against the virus as it evolves into new strains. Subsequent vaccines are always much easier to develop than the first one to combat a disease.

The second problem is that HIV likes to mutate a lot more than other diseases seem to, which would greatly decrease the effectiveness of a traditional vaccine since creating a vaccine that was only effective for one or two strains, without taking the others into account, would only offer partial protection against the possibility of becoming infected, a protection which would become increasingly incomplete as the number of new strains you weren't vaccinated against increased.

You also have to couple that with the fact that HIV doesn't go through the usual routes of transmission. Vaccines work by pre-empting your body's immune response. Instead of waiting for you to fight off an illness so your body's immune system can engineer a pattern on which to build its antigens to destroy the virus, vaccines simply supply it the blueprints so the first time you come into contact with the virus itself, your body already has the ability to produce the specific antigens to destroy it without you getting sick.

That's all well and good, except HIV starts off by specifically infecting and destroying the cells which do that, so even if you supply them with the blueprint, by the time the body knows its under attack, it's too late for it to do anything about it.

So, all that put together means we have to be quite a bit trickier than usual in creating an effective advance defense for the little bugger so we don't have to worry about contracting it... but like I said, it only took us twenty-five years or so to figure it out from the first time HIV appeared, so we've actually done pretty well on that road.

Answer 2

AIDS vaccines are difficult to develop because HIV infects CD4+ T-cells, the very same cells that are important in forming an immune response to a vaccine

Answer 3

Traditional vaccines are usually dead samples of the virus injected into the body so it can develop antibodies. Since that didn't work, we need to use alternate means that will eliminate or neutralize the virus while still maintaining adequate health for the host body. That is not yet feasible.... maybe in the near future.

Until then, practice safe sex!

Answer 4

Simply because they haven't found one yet. I believe they will eventually find one, whether it be a year from now, 10 years, or even 100. Scientists will find a vaccine someday.

Answer 5

Human immunodeficiency virus (commonly known as HIV, and formerly known as HTLV-III and lymphadenopathy-associated virus) is a retrovirus that primarily infects vital components of the human immune system such as CD4+ T cells, macrophages and dendritic cells. It also directly and indirectly destroys CD4+ T cells. As CD4+ T cells are required for the proper functioning of the immune system, when enough CD4+ T cells have been destroyed by HIV, the immune system functions poorly, leading to the syndrome known as AIDS.
HIV is different in structure from previously described retroviruses. It is around 120 nm in diameter (120 billionths of a meter; around 60 times smaller than a red blood cell) and roughly spherical.

HIV-1 is composed of two copies of single-stranded RNA enclosed by a conical capsid, which is in turn surrounded by a plasma membrane that is formed from part of the host-cell membrane. Other enzymes contained within the virion particle include reverse transcriptase, integrase, and protease.

HIV has several major genes coding for structural proteins that are found in all retroviruses, and several nonstructural ("accessory") genes that are unique to HIV. The gag gene provides the physical infrastructure of the virus; pol provides the basic enzymes by which retroviruses reproduce; the env gene supplies the proteins essential for viral attachment and entry into a target cell. The accessory proteins tat, rev, nef, vif, vpr, and vpu enhance virus production. Although called accessory proteins, tat and rev are essential for virus replication. In some strains of HIV, a mutation causes the production of an alternate accessory protein, Tev, from the fusion of tat, rev, and env.

The gp120 and gp41 proteins, both encoded by the env gene, enable the virus to attach to and fuse with target cells to initiate the infectious cycle. Both, especially gp120, have been considered as targets of future treatments or vaccines against HIV.

One of the major characteristics of HIV is its high genetic variability as a result of its fast replication cycle and the high error rate and recombinogenic properties of reverse transcriptase. This means that different genomic combinations may be generated within an individual who is infected by genetically different HIV strains. Recombination results when a cell is simultaneously infected by two different strains of HIV and one RNA transcript from two different viral strains are encapsidated into the same virion particle. This virion then infects a new cell where it undergoes replication. During this phase, the reverse transcriptase, by jumping back and forth between the two different RNA templates, will generate a newly synthesized retroviral DNA sequence that is a recombinant between the two parental genomes. This recombination is most obvious when it occurs between subtypes.

Three groups of HIV-1 have been identified on the basis of differences in env: M, N and O [35] (Figure 4). Group M is the most prevalent and is subdivided into eight subtypes, based on the whole genome, that are each geographically distinct.[36] The most prevalent are subtypes B (found predominantly in North America and Europe), A and D (found predominantly in Africa), and C (found predominantly in Africa and Asia) (Figure 5); these subtypes form branches in the phylogenetic tree representing the lineage of the M group of HIV-1 (Figure 4). Coinfection with distinct subtypes gives rise to circulating recombinant forms (CRFs).

In 2000, the last year in which an analysis of global subtype prevalence was made, 47.2% of infections worldwide were of subtype C, 26.7% were of subtype A/CRF02_AG, 12.3% were of subtype B, 5.3% were of subtype D, 3.2% were of CRF_AE, and the remaining 5.3% were composed of other subtypes and CRFs[37] (Figure 5). Almost 95% of all HIV research currently taking place is focused on subtype B, while a few laboratories focus on other subtypes

Because of this nature it is not possible to produce an effective vaccine against the HIV

Answer 6

there is not a vaccine yet because none of our government officals or their families have the virus, therefore, there is no sense of urgency in their minds to find one.

Answer 7

Because the non profit organizations have to worry about next year's budget.